Applications executing within a network environment frequently utilize “keep alive” messaging schemes to monitor operational status of other applications within the network. For example, applications executing on network devices within network environment send periodic packets to each to confirm connectivity and to indicate operational status of each device. These periodic packets are sometimes referred to as “keepalives” or “hellos.” For example, a first application executing on one network device may send periodic packets to a peer application executing on another network device every 50 milliseconds (ms) to indicate that the first application is still operational. Likewise, the application may detect reception of corresponding periodic packets from the peer application within the same period of time (e.g., 50 ms). When a threshold number of packets have not been received in the allotted time frame, the application determines that a session failure event has occurred, such as failure of the network device on which the peer application is executing, failure of a link or node connecting the two network devices or failure of the application itself. In response to the failure, the network device on which the peer application is executing may take certain actions, such as redirecting communications to a different peer application.
As one example, routers may exchange periodic packets by establishing a session provided by the bidirectional forwarding detection (BFD) protocol. In accordance with BFD, a first router periodically sends BFD packets at a negotiated transmission time interval and detects a session failure event when the router does not receive a BFD packet from a second router within session detection time interval. For instance, a router may negotiate to receive BFD packets every 50 ms from a peer router and may independently utilize a detection multiplier of three (3) times that interval, i.e., 150 ms in this example, for detecting failure. If the receiving router does not receive a BFD packet from the peer router within the 150 ms session detection time interval, the receiving router detects a connectivity failure with respect to the second router. Consequently, the receiving router may update its routing information to route traffic around the second router. Further details of the BFD protocol may be found in the proposed standard for BFD, by D. Katz and D. Ward (Juniper Networks, June 2010, ISSN: 2070-1721), the entire content of which is incorporated herein by reference.